Ergonomic tubes, so-called ergo tubes, are known which allow for variable heights, angles, and distances in ergonomically favorable positions. These assemblies are very elaborate and, as a result, also very expensive. Simpler ergo tubes solely allow for adjustments in height and angle. Therefore, said tubes are also more cost-efficient but do not fulfill all requirements.
From DE 10 2004 006 937 A1, a tube for a microscope is known, wherein the ergonomic function is realized by means of a tilting mirror. Said mirror is swiveled half as fast as the tube viewer. The correct image orientation is achieved via a second mirror. The additional space required due to both mirrors is created by means of an elaborate tube lens design, which shifts the principal planes. The back focus of the individual tube lens system is elongated by a factor of up to 1.25. Such optics designs inevitably cause problems with the image quality, whereby particularly the position of the exit pupil is affected negatively. Vignetting and lateral chromatic aberrations occur.
DE 195 13 870 C2 describes a binocular microscope with a lens corrected to infiniti, and a downstream two-lens tube lens unit with a back focus of more than 200 mm. Thereby, the lens on the side of the object is a diffuser lens made of flint glass with Abbe numbers between 43 and 47. The lens away from the object is a condenser lens made of crown glass with Abbe numbers between 65 and 69. A reverse configuration of the two lenses of the tube lens unit is also described.